The present invention relates generally to mechanical devices used in surgical procedures to obtain ligation or hemostasis, and more particularly, to low profile tools that can apply a preformed, spring loaded ligation clip used during surgery to clamp around a vessel or duct, such as the cystic duct, and thereby obtain ligation.
It will be appreciated by those skilled in the art that the use of ligation clips to control bleeding during surgical procedures is well known. As described, for example, in U.S. Pat. Nos. 4,976,722 and 4,979,950, prior art clips are generally formed of metal wire, usually a titanium alloy, having a "U-shaped" rectangular cross-section. Such prior art clips often include a grooved pattern machined into the inner or clamping surfaces of the clip, in an attempt to enhance the ability of the clip to remain in position after it is closed around the vessel. Application of the clip to the vessel is normally effected by means of a crushing action produced by a clip applier, such as that disclosed in U.S. Pat. No. 5,030,226. Such crushing actions, of course, permanently deform the clips, making them difficult to remove or re-position.
Prior art surgical ligation clips have several inherent problems. For example, the force applied by the clip to the vessel can be variable and inconsistent from one clip to the next, because of the variation in crushing force applied to the clip by the user. Further, prior art clips have a tendency to slip off the end of the blood vessel stub (i.e., parallel to the axis of the vessel) to which it has been applied, because of the low coefficient of friction associated with the clip, and lack of adequate restraining force provided by the clip. Because of this, separation of the clip from the vessel to which it has been applied, after the wound has been closed, is not uncommon. A related problem found in the prior art is the fact that the ligating or restraining force offered by the crushed clip varies along the length of the clip, decreasing toward the open end. Thus, the section of the vessel near the open end of the clip can be inadequately ligated.
It is also common in the prior art to actually form and crush the clip only at the time of its application to the targeted blood vessel. It is often required that vessels of 4 mm and larger diameter be ligated. Because most clips of the prior art have no spring action it is required that the inside clearance dimension of the clip, prior to crushing, be larger than the vessel. This does not lend itself to clip applier designs that will pass through small 5 mm trocars. Accordingly, the clip applier mechanism of the prior art must be relatively large and cumbersome. This is a particular problem in laparoscopic procedures, during which both the clip and clip applier must be inserted through a trocar placed through the patient's external tissues and into the surgical field. Thus, prior art ligation clip appliers used in laparoscopic procedures universally consist of a 10 mm diameter clip applier that can fit only through a trocar having a 10 to 11 mm diameter entry port. Because one goal of laparoscopic surgery is to minimize the size of the entry wound, a surgical ligation clip and clip applier that can be used within a 5 mm diameter trocar port is highly desirable.
To address these problems, a new and improved surgical clip was designed, as illustrated in FIGS. 1 and 2 and in U.S. patent application Ser. No. 08/111,634 filed on Aug. 25, 1993. The improved clip has a vessel clamping arm, a vessel support member, and at least one tension coil integrally joining the arm and support member. The clip is pre-formed so that in its equilibrium state, it can be easily placed within the surgical field, including through an endoscopic trocar port with as little as a five millimeter diameter. After the clip is placed proximate the blood vessel or duct to be clamped, the clamping arm is moved from its equilibrium position to a position under higher tension, allowing positioning of the vessel between the arm and support member. When correct placement and positioning is achieved, the arm is released and, as the arm tends to move back towards its equilibrium position, it clamps the vessel between the arm's curved lower surface and the supporting upper surface of the vessel support member.
To enhance the performance of the tension coil(s), the vessel support member includes first and second arms, one of which terminates in a loop section. Minimal cross-sectional area of the clip is achieved by substantially longitudinally aligning the vessel support member, the clamping arm, the loop section, and the tension coil.
The clamping arm is pre-formed into an equilibrium that generally aligns with the horizontal plan of the support member. A second embodiment of the clip pre-loads the clamping arm into a relaxed position where the free end of the arm rests against the upper surface of the support member.
Unfortunately, several problems are encountered in applying this novel pre-formed, spring-action ligating clip on to a vessel through a 5 mm trocar port. First, the nominal 5 mm cross section of the clip that is inserted through the trocar places severe design restrictions on any applier mechanism. Traditional "crush type" clips require a crusher and anvil type applier mechanism which is too large to pass through a 5 mm trocar. Second, care must be taken so that the elastic limit of the spring material is not exceeded when the clip is opened up so that it can be placed over the vessel diameter. For titanium wire of diameter 0.75 mm, for example, lifting the distal end of the center leg of the spring much above 2 mm will exceed the elastic limit.
What is needed, then, is a clip applier tool that be used to place a pre-formed, spring action ligation clip around a large diameter vessel without permanently deforming or weakening the clip, one that will compress, without crushing, the vessel, and yet be small enough to use in through a 5 mm trocar.